 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
 #include <ctype.h>

 int main(int argc, char **argv) {
     
	int sum = 0, a, b, flag = 0;
	 	
	for ( int i = 1; i < argc; i++) 
	{
			for (int j = 0; j < (strlen(argv[i])); j++)
			{		 
				if( !isdigit(argv[i][j]) && argv[i][j] != '-' && j == 0 ){
					printf("\"%s\" is not number\n", argv[i]);
					j = (strlen(argv[i]) - 1);
					flag = 1;
				} 
				else if( !isdigit(argv[i][j]) && j != 0 ){
					printf("\"%s\" is not number\n", argv[i]);
					j = (strlen(argv[i]) - 1);
					flag = 1;
				} 
			}
			
		if ( i == argc - 1  && flag == 1)
		{
			printf("Usage: numbers\n");
		}
	} 
	
	if( argc == 1 && flag == 0 ) 
	{
		printf("Usage: numbers\n");
		return 0;
	}  
	 
	for (int i = 1; i < argc; i++)
	{
		sscanf(argv[i], "%d", &a);
		sum += a;
	}
	
	if ( flag == 0){
		printf("%d\n", sum);
	}
   
    return 0;
 }